Aporox 5cm across 
Merkaba, also spelled Merkabah, translates literally to light, spirit, body. The Merkaba Symbol is a shape made of 2 intersecting tetrahedrons.
Discovered in the Republic of Karelia near Lake Putkorezo shungite is a rock formation that's believed to be about two billion years old, said to be the “miracle stone” and/or “the stone of life,"
Its said to shield you from the electromagnetic radiation given off by electrical equipment, including computers,mobiles and other electronic devices. The composition of the stone is almost 98% carbon, with a 3.5-4 on the Mohs scale of hardness.

Merkaba Shungite